1. Field of the Invention
The present invention relates to data sharing equipment for mobile stations, which comprises a plurality of mobile stations moving along runways and a monitor station for monitoring the plurality of mobile stations, and more particularly to data sharing equipment for mobile stations for efficiently delivering data shared among the mobile stations.
2. Description of the Related Art
Equipment for sharing data among a plurality of mobile units is known described in Japanese Patent Application Laid-Open No. 4-319991. Such equipment provides an operation schedule of each mobile unit, and states of roads and traffic to a destination of the mobile unit from central control equipment to the mobile unit. Thus, the mobile bodies can be guided by such information.
But, when the central control equipment and the mobile unit communicate mutually, this equipment has to transmit a large volume of data every time data is needed, resulting in increasing a load upon a communication line.
In addition, there is also used widely a system which provides a plurality of work machines at mines and construction sites with guidance on works by means of positioning equipment such as GPS and a total station. These work machines share data, which indicates the present landform, target landform, work schedule and work progress, to proceed the work. When the number of work machines is not many, each of data may be transmitted directly from a central station to the work machines. But, when the number of work machines is increased, data must be transmitted to the plurality of work machines, and a load upon the communication line is increased accordingly, making it hard to transmit individually. And, since the data transmission is started when data is required, the work machine has to stop working while the data is transmitted and received. Thus, there is a wasted standby time.
To decrease the communication load, broadcasting may be used to transmit to all the vehicles, but since the central station does not receive any response from the receiving side, it cannot be confirmed whether the communications are completed properly or not.
Such a problem can be solved by transmitting and receiving data by a communication method which requires an acknowledgment of reception (ACK). This communication method includes point-to-point communication and multicasting.
The point-to-point communication requires the central station to communicate with each of the plurality of work machines and takes much time to do so. And, a load on the communication line is increased because the central station receives an acknowledgment of reception from the work machines.
The multicasting can transmit data from the central station to the plurality of work machines in the same way as the broadcasting, but a load upon the communication line is increased because the central station receives an acknowledgment of reception from the plurality of work machines in the same way as the point-to-point communication.
Besides, a plurality of work machines working together may have inconsistencies in data among the plurality of work machines, resulting in causing a trouble. For example, it is assumed that track A is moved along course a and loaded by loading machine B. When the next truck C is to be loaded, the operator of the loading machine B presumes that the truck C runs the same course a as the truck A did and operates the loading machine B to stand by. But, it may happen that the truck C approaches through a different course a1, and the loading machine B and the truck C may collide mutually.
In such a case, it is possible to use the multicasting so to transmit simultaneously to all the vehicles (work machines) and to separately receive an acknowledgment of reception from all the vehicles. But, a load on the communication line is increased because of the acknowledgments of reception from the plurality of vehicles.
It is also necessary to transmit data again when there is no acknowledgment of reception from a vehicle which does not need the data at all because it is far away.
Furthermore, by selectively transmitting to vehicles which may need data, an acknowledgment of reception may be received from those vehicles. But, it is hard to predict which vehicles need data, and if such prediction is not correct, there is a danger of causing an accident that such vehicle colloid each other.
Under the circumstances as described above, it is an object of the invention to provide data sharing equipment for mobile stations which suppresses a load on a communication line for data communications between a monitor station and mobile stations and to reduce a standby time required for data communications of the mobile stations.
To achieve the aforethe object, a first aspect of the invention is directed to data sharing equipment for mobile stations, comprising a plurality of mobile stations moving along runways and a monitor station for monitoring the plurality of mobile stations, wherein:
the plurality of mobile stations and the monitor station are provided with communication means for transmitting and receiving data to and from other stations;
the mobile stations are provided with storage means for storing data transmitted from other stations, and the monitor station or at least one of the plurality of mobile stations are provided with imparting means for giving identification information to predetermined data for identifying the predetermined data;
predetermined instructions are given to the mobile station with identification information given by the imparting means; and
the mobile station instructed by the identification information, when data corresponding to the identification information is not stored in its storage means, transmits a demand for transmission of data corresponding to the identification information to the monitor station or other mobile station through the communication means.
A second aspect of the invention is directed to the data sharing equipment for mobile stations according to the first aspect of the invention, wherein:
the monitor station is provided with data storage means for storing data as a reference and identification information imparting means for giving identification information for identifying data to the data stored in the data storage means, and transmits the data stored in the data storage means and the identification information given to the data to the plurality of mobile stations by broadcasting;
the monitor station or any one of the plurality of mobile stations transmits predetermined instructions to other stations by the identification information; and
the mobile station instructed by the identification information, when data corresponding to the instructed identification information is not stored in the own storage means, transmits a demand for transmission of data corresponding to the identification information to the monitor station or other mobile stations.
A third aspect of the invention is directed to the data sharing equipment for mobile stations according to the first aspect of the invention, wherein:
the monitor station is provided with data storage means for storing data as a reference and identification information imparting means for giving identification information for identifying data to the data stored in the data storage means, and transmits latest identification information given to latest data stored in the data storage means by the identification information imparting means to the plurality of mobile stations by periodically broadcasting through the communication means; and
when the latest data corresponding to the latest identification information from the monitor station is not stored in the storage means and judges that the latest data is required, the mobile station transmits a demand for transmission of the latest data to the monitor station or other mobile stations through the communication means.
A fourth aspect of the invention is directed to the data shearing equipment for mobile stations according to the first, second or third aspect of the invention, wherein each of the plurality of mobile stations comprises first communication means for transmitting and receiving data with other mobile stations and second communication means for transmitting and receiving data with the monitor station.
A fifth aspect of the invention is directed to data sharing equipment for mobile stations, which comprises:
a plurality of unmanned mobile stations which run according to specified course data and perform predetermined works;
generation means which generates a portion or all of course data indicating a predetermined course to be run according to the progress of work by at least one unmanned mobile station among the plurality of unmanned stations;
imparting means which gives identification information for identifying course data to the course data generated by the generation means;
transmission means which transmits the course data to which identification information is given by the imparting means to the plurality of unmanned mobile stations in advance; and
instruction means which instructs a predetermined course to be run by transmitting identification information corresponding to course data indicating the predetermined course to an unmanned mobile station which is to enter the predetermined course after deciding a time to enter the course or an order to enter the course.
The first to fifth aspects of the invention will be described with reference to FIG. 9.
Monitor station 20 stores course data C1 and gives course ID, e.g., ID1, to the course data C1, and also broadcasts the course data C1 and the course ID1 to respective vehicles (e.g., excavator 60, truck 10 and truck 11) by UHF (S11).
When the excavator 60 moves to a dotted line position indicated by point 60A to which the aforethe course 2 is applied, course data C2 corresponding to the course 2 is produced, and the course data C2 is transmitted to the monitor station 20. After storing the course data C2, the monitor station 20 gives course ID, e.g., ID2, to the course data C2. Since the latest course ID only is stored, the course ID is updated its stored contents to become the course ID2.
The course data C2 and the course ID2 are broadcast from the monitor station 20 to the excavator 60, the truck 10 and the truck 11 by UHF (S12).
Besides, the same processing as above is performed when the excavator 60 moves to a point (a dot-lined position indicated by 60B) to which the aforethe course 3 is applied. Specifically, for example course ID3 is given to the course data C3, the stored content of the course ID is updated to the latest course ID3, and the course data C3 and the course ID3 are broadcast to the respective vehicles (S13).
In the processing up to this point, it is assumed that the excavator 60 and the truck 10 receive all the course data C1 to C3 and the course ID1 to ID3, and the truck 11 receives the course data C1, C2 and the course ID1, ID2 only.
Here, when the excavator 60 returns from the point where the course 3 is applied to the point where the course 2 is applied, the course ID2 is transmitted to the monitor station 20 because the course data is already produced as the course data C2 and transmitted to the monitor station 20.
At this time, after recognizing that the excavator 60 has moved from the course 3 to the location where the course 2 shall be adopted, the monitor station 20 transmits the course ID2 as the instruction content to another vehicle, e.g., the truck 10 (S14).
The truck 10 having received the course ID2 judges that it already has the course ID2 and is controlled to run according to the course data C2 indicated by the course ID2.
The excavator 60 moves from the present course 2 to a position where the course 3 is adopted, the truck 11 has reached a loading spot, and the SS radio communications between the excavator 60 and the truck 11 become possible. Then, the excavator 60 transmits the course ID3 as the instruction content to the truck 11 by the SS radio communication (S15). The truck 11 judges that it does not have the instructed course ID3 and demands for the course data C3 by transmitting the course ID3 to the excavator 60 by the SS radio transmission (S16).
The truck 11 which has received the course data C3 transmitted from the excavator 60 which has responded to the demand stores the course data C3 and the course ID3 and is controlled to run according to the course data C3 (S17).
According to the first aspect of the invention, data and the identification information indicating the data are transmitted to the mobile stations, and the actual instructions are conducted by transmitting the identification information to the pertinent mobile station. Therefore, a load on the communication line can be suppressed when the instructions are given to the plurality of mobile stations. If the mobile station to be instructed does not have the instructed date, it can obtain the data from another mobile station. Therefore, a load on the monitor station and a load on the communication line between the monitor station and the mobile station can be decreased.
According to the second aspect of the invention, data is previously transmitted to the mobile stations by broadcasting and the instructions are transmitted with the identification information to the mobile stations. Therefore, the instructions required to actually execute the instruction contents can be sufficiently executed by transmitting the identification information in a small volume of data, and a load on the communication line can be suppressed.
Since a large volume of data is previously transmitted, identification information in a small amount of data only is received when the instructions are actually received. Thus, a standby time of the mobile station can be decreased.
According to the third aspect of the invention, the latest identification information is transmitted by broadcasting in order to update to the latest data, the mobile station which has judged it necessary can demand the monitor station or another mobile station for the latest data to suppress the amount of communication data and to suppress a load on the communication line.
According to the fourth aspect of the invention, the communications between mobile stations and the communications between the monitor station and the mobile station are performed by separate communication means, so that a load on the communication line between the monitor station and the mobile station can be suppressed by performing the communication of a large volume of data between the mobile stations.
According to the fifth aspect of the invention, the mobile station to be instructed is previously transmitted with a large volume of data in advance, and when it is actually instructed, it receives identification information in only a small volume of data, so that a standby time of the mobile station can be decreased.